investigators describe the vehicle as an suv 1997 through 2002 ford expedition they believe with damage to the passenger side headlight. the hood and passenger side front quarter panel. >>> continuing our conversation on the explosions at the boston marathon, i'm joined now by security expert ed clark who's been sharing his insights with us since the explosions yesterday. good to have you back here. some of the latest information, we've heard about an unexploded bomb found at the scene and heard about two more unexploded bombs. what have you heard the latest and what information could we glean from this unexploded devices? >> if they recover the unexploded devices, this he can do a forensic analysis between that devase and the two that detonated. it allows investigators to draw a link in analysis. >> get a signature of who the bomber is. >> absolutely correct. >> in the past we had you on to talk about incidents like this around the world and in the u.s. we talk about chatter and the chatter that goes on before, during and after and we've not been hearing any of that chatter. the only t